In vehicle construction, stringent requirements are being increasingly imposed on the strength and rigidity of body parts. At the same time, however, in the interest of minimizing weight, a reduction in the material thickness is aimed at. High-strength and super-high-strength materials offer a solution in order to meet the conflicting requirements, these materials permitting the production of components of very high strength with at the same time a small material thickness. By a suitable selection of process parameters during conventional hot forming in the case of these materials, strength and toughness values of the component can be specifically set.
Such a material is, for example, the pre-coated boron steel sold by Usinor under the trade name Usibor 1500. The steel is provided with an AlSi coating, which, inter alia, exhibits advantageous corrosion-inhibiting properties in the course of the subsequent heat treatment.
To produce such a component by means of hot forming, first of all a sheet blank is cut out of a coil, this sheet blank is then heated above the structural transformation temperature of the steel materials, above which the material structure is in the austenitic state, is inserted in the heated state into a forming tool and is formed into the desired component shape and is cooled down while the desired forming state is mechanically fixed, tempering or hardening of the component being effected.
The component is often subjected to a pre-forming step or a trimming step before the actual hot forming. This is described, for example, in DE 101 49 221 C1. However, such a method may result in problems with regard to corrosion, since coil coating normally applied is damaged during the pre-forming. Conventional pre-forming and trimming of the components, especially in the case of pre-coated high-strength steels such as Usibor 1500 PC, which has an AlSi coating, is therefore omitted.